291260 2025-04-08 03:11:59 -0700 [css-anchor-position-1] Subtree invisible when anchor-centered element visibility changes 2025-05-13 12:32:48 -0700 1 1 1 Unclassified WebKit Layout and Rendering WebKit Nightly Build Unspecified Unspecified RESOLVED DUPLICATE 291065 InRadar P2 Normal --- 291856 1 plampe kiet.ho bfulgham ian kiet.ho koivisto simon.fraser webkit-bug-importer zalan oldest_to_newest 2109689 0 474868 plampe 2025-04-08 03:11:59 -0700 Created attachment 474868 small demo to reproduce the issue Given anchor positioning is used and anchor target uses 'anchor-canter' without using anchor() function for any insets, When anchor target visibility changes (it becomes visible after being invisible i.e. display:none changes to e.g. display:flow), Then the anchor target subtree is not rendered (no RenderObjects are created) and hence no anchor target children are visible. I did some digging and it actually is a regression that was introduced here: https://github.com/WebKit/WebKit/commit/aa6b7858fefa58b92a4ba4da1df0b837fb5cf1c6 (Antti Koivisto: [css-anchor-position-1] Trigger evaluation of default anchor when it's used for anchor-center (https://bugs.webkit.org/show_bug.cgi?id=283295)) Small test case attached. WPT test case is up for review: https://github.com/web-platform-tests/wpt/pull/51892 2109743 1 webkit-bug-importer 2025-04-08 11:01:31 -0700 <rdar://problem/148840557> 2116848 2 kiet.ho 2025-05-13 12:32:48 -0700 Confirmed dupe of 291065. *** This bug has been marked as a duplicate of bug 291065 *** 474868 2025-04-08 03:11:59 -0700 2025-04-08 03:11:59 -0700 small demo to reproduce the issue 6-min-repro.html text/html 750 plampe PGh0bWw+CiAgPGhlYWQ+CiAgICA8c3R5bGU+CiAgICAgIC5idXR0b24gewogICAgICAgICAgYW5j aG9yLW5hbWU6IC0tbWVudTsKICAgICAgfQogICAgICAubWVudSB7CiAgICAgICAgICBwb3NpdGlv bjogZml4ZWQ7CiAgICAgICAgICBwb3NpdGlvbi1hbmNob3I6IC0tbWVudTsKICAgICAgICAgIC8q IHRvcDogYW5jaG9yKGJvdHRvbSk7ICovCiAgICAgICAgICBoZWlnaHQ6IGF1dG87CiAgICAgICAg ICBtYXJnaW46IDA7CiAgICAgICAgICBwYWRkaW5nOiAwOwogICAgICAgICAgb3ZlcmZsb3c6IGF1 dG87CiAgICAgICAgICBiYWNrZ3JvdW5kLWNvbG9yOiByZWQ7CiAgICAgICAgICBqdXN0aWZ5LXNl bGY6IGFuY2hvci1jZW50ZXI7CiAgICAgICAgICBkaXNwbGF5OiBub25lOwogICAgICB9CiAgICA8 L3N0eWxlPgogIDwvaGVhZD4KICA8Ym9keT4KICAgIHh4eCB5eXkgenp6PGJ1dHRvbiBpZD0iYnV0 dG9uIiBjbGFzcz0iYnV0dG9uIj5NZW51PC9idXR0b24+CiAgICA8ZGl2IGlkPSJtZW51IiBjbGFz cz0ibWVudSI+CiAgICAgIDxsaT5Mb3JlbTwvbGk+CiAgICAgIDxsaT5JcHN1bTwvbGk+CiAgICAg IDxsaT5Eb2xvcjwvbGk+CiAgICA8L2Rpdj4KICAgIDxocj48aHI+PGhyPgogICAgPHNjcmlwdD4K ICAgICAgcmVxdWVzdEFuaW1hdGlvbkZyYW1lKCgpID0+IGRvY3VtZW50LmdldEVsZW1lbnRCeUlk KCdtZW51Jykuc3R5bGUuZGlzcGxheSA9ICJmbG93Iik7CiAgICA8L3NjcmlwdD4KICA8L2JvZHk+ CjwvaHRtbD4K